LCD TV is capable of delivering on a large screen a realistic, high-image quality viewing experience. However, on a large LCD panel, the image distortion near the edge and the low contrast ratio based on the viewing angles become an issue that requires attention. As a solution, the industry has come up with a curved display panel. A curved LCD panel offers an improved image quality as regard to the image distortion without sacrificing the contrast ratio.
An LCD panel has a CF substrate, a TFT substrate and a liquid crystal layer between the CF substrate and the TFT substrate. As illustrated in FIG. 2A, the TFT substrate 20 has a pixel electrode layer 21, a passivation layer 22, a plurality of data bus lines 23 and a gate insulator layer 24 to form a plurality of pixel areas 32 arranged in a two-dimensional array. The CF substrate 71 has common electrode layer 79 and a color filter layer 74 having a plurality of filter cells 75, 76, 77, each of which is corresponding to a pixel area 32. The pixel area and the corresponding filter cell are generally referred to as a pixel. The TFT substrate 20 also has a plurality of bordering areas 34 located between two adjacent pixel areas 32. It is desirable to have a pixel area as large as practically possible. That is, it is desirable to have the width of the bordering areas as small as possible.
In a color display, each pixel has three color sub-pixels. Each of the color sub-pixels has a different filter cell and a different pixel area. Each TFT pixel area is used to control the transmission of light through the liquid crystal layer 40 in the color sub-pixel. In order to prevent light in the bordering area or opening from leaking into neighboring filter cells, a masking element known as “BM” 72 is disposed between two adjacent filter cells. Ideally, the width of the masking element is substantially the same as the width of the bordering area 34. As such, the aperture 73 is optimal. When the masking element is in perfect alignment with the corresponding opening, the attainable contrast ratio of the display is also optimal.
In a flat screen TV, the spatial relationship between the filter cell and the corresponding pixel area is substantially the same regardless of the locations of the pixels. For example, on a flat screen TV as shown in FIG. 1A, the pixels at location A and the pixels at location B are practically identical.
In making a liquid crystal display, all of the component panels, especially the CF substrate and the TFT substrate, are firmly sealed so as to maintain the perfect alignment between the filter cell and the corresponding pixel area. When a flat screen display panel is bent to make a curved screen display panel, the CF substrate and the TFT substrate are bent together. Because the radius curvature of the CF substrate and the radius curvature of the TFT substrate in a curved display panel are slightly different, there would be a local shift between the filter cell and the corresponding pixel area. As a result, the masking element on the CF substrate may not be in perfect alignment with the corresponding opening on the TFT substrate. The amount of shift is dependent upon the locations of the pixels (see FIG. 1B). For example, while the pixels at location A may have no shift or the shift is negligible (see FIG. 2A), the shift S at location B might result in a substantial misalignment between the masking element and the corresponding opening. The misalignment may cause the light 113 transmitted through the bordering area to leak into a neighboring filter cell as shown in FIG. 2B. In order to eliminate or minimize the light leak due to the misalignment, a broader masking element 72′ is used (see FIG. 2C). A broader masking element, however, results in a smaller aperture 73′ and, therefore, a lower contrast ratio.